Portable electronic devices, such as two-way radios, typically use an energy source, for example a battery, to derive power necessary for operation. A battery can comprise a single battery cell or a plurality of battery cells arranged in various fashion, for example, in series, parallel, or a combination of series and parallel.
When an electronic device, such as a radio, is subjected to shock or vibration, for example when dropped, any movement of the battery cells created by the impact of the drop can cause a momentary loss of power and result in unpredictable operation of the radio. During the drop, a physical connection of one battery cell to another (or to the radio) can become momentarily broken or opened, causing a dysfunction or total loss of power to the device. An important point which must be considered in the case of some portable communication devices, such as radios, is the mass of the energy source is a large proportion of the total mass of the device. This creates problems in the design of a system to effectively retain the battery and cells in a consistent position during operation in all possible orientations and modes.
Battery cells are typically cylindrically- or rectangularly-shaped and include positive and negative electrical contact surfaces at their ends. Consequently, the battery cell is generally located in a cylindrical or rectangular chamber formed within a battery housing. Typically, the inter-cell connections are provided by welding metal tabs between the cells.
In order to make an energy source having the highest energy density in the smallest package, all of the interior volume of the housing should be filled with the battery cells. This has led to the development of prismatic or rectangular battery cells that efficiently fill cubic- or square-shaped housings. However, these cells are rather expensive and not readily available on the mass consumer market. Typically, cylindrical battery cells are used and a significant portion of the housing interior volume is wasted due to the attempt of placing round cells in a square housing. However, this loss of energy density or efficiency is typically offset by the lower cost of the cylindrical cells versus the prismatic cells. When using cylindrical cells, special techniques must be used to maintain the cells in position during drop, requiring even more space in the housing. These positioning devices reduce the overall volume utilization of the package, degrading the efficiency and increasing the package size.
In the prior art, the battery cells are typically held in place and kept from moving by dispensing a bead of hot-melt adhesive in the channel in between the neighboring cells. This method of dispensing hot-melt is messy and slow and results in an inconsistent battery package which does not provide the high degree of reliability desired.
Clearly, what is needed is a method of providing a high-efficiency, high-energy density package at a low cost.